1. Field of the Invention
The present invention relates to a method and apparatus for maintaining a vehicle screen such as for example a vehicle headlamp.
2. Description of the Related Art
Vehicle screens such as headlamp lenses and windscreens require cleaning in order to retain their translucent properties. As dirt is deposited and collects on the surface of the screen the amount of light passing through the screen is diminished. In the case of a windscreen this reduces visibility. In headlamp applications deposited dirt on the lens can form a reflective layer as well as reducing light output. Light can therefore be reflected back towards the reflector and out of the headlamp in undetermined directions thereby causing glare. This problem is exacerbated by the heating effect caused by the light beam. As liquid contacts the headlamp lens, the beam tends to heat and thereby evaporate the liquid leaving any dirt previously suspended in the liquid on the surface of the headlamp. This so-called xe2x80x9cburn-onxe2x80x9d effect can increase the glare from a headlamp substantially.
Numerous techniques have been suggested in the past for overcoming these problems. Some of these solutions have used wipers to remove the dirt often requiring some form of water nozzle to spray water or cleaning liquid onto the screen surface prior to wiper action.
Problems are associated with many of these solutions. For example, they are prone to mechanical failure of the wiper components and to a cleaning liquid reservoir becoming empty since the liquid is not recycled but is lost as soon as it is sprayed. Furthermore, the driver is usually required to take positive action to clean the screen.
It is therefore an object of the present invention to at least partly mitigate the difficulties of the prior art.
According to a first aspect of the present invention there is provided a method of maintaining a surface of a translucent screen of a vehicle comprising the steps of providing a first edge region of said screen surface with liquid, causing the liquid to flow across the surface from the first edge region in the direction of a second edge region, and collecting said liquid in said second edge region, whereby said first edge region is selected from a top edge region and a bottom edge region, located below said top edge region, in response to said detected vehicle velocity.
According to a second aspect of the present invention there is provided apparatus for maintaining a vehicle screen supported with respect to a structure by a gasket, said screen having a first and second edge region, said gasket having first conduit means having an opening proximate to said first edge region and second conduit means having an opening proximate to said second edge region, wherein said structure is a vehicle and said screen is a headlamp screen and said first edge region is disposed below said second edge region, and wherein the system further comprises supply apparatus connectable to said first conduit means for supplying a liquid thereto and collection apparatus connectable to said second conduit means for collecting said liquid.